Deformation of Mauna Loa volcano before, during, and after its 2022 eruption

Mauna Loa volcano on the Island of Hawaiʻi erupted on 27 November 2022, marking the end of decades-long volcanic unrest since its last eruption in 1984. Here we briefly describe the evolution of the USGS Hawaiian Volcano Observatory’s geodetic monitoring network and show patterns of deformation as measured by Global Navigation Satellite Systems (GNSS), interferometric synthetic aperture radar (InSAR), and borehole tilt in the years leading up the 2022 eruption. We highlight the long-term buildup as well as the imminent pre-eruptive geodetic signals, including subtle changes observed in early 2021 that suggested an eruption might be near, and the significant ramp up of activity in September 2022 that provided strong evidence of likely impending eruptive activity. Of particular importance are the first borehole tilt excursions related to magma movement measured at Mauna Loa’s summit, which began in 2021 and were accompanied by increased rates of seismicity. In addition to describing the evolution of surface displacements, we also model the co-eruption deformation, which can be fit by dike opening that matches the geometry of the surface eruptive fissures. Geodetic data associated with Mauna Loa’s pre-, co-, and post-eruptive phases provide opportunities for exploring questions related to the volcano’s history and magmatic system. How does the 2022 eruption compare to previous eruptions in 1975 and 1984? What geodetic tools are best suited for tracking volcanic unrest at Mauna Loa? How does caldera faulting relate to eruption timing? What, if any, are the relations between Mauna Loa and neighboring volcano, Kīlauea, which paused in its own eruptive activity as the Mauna Loa eruption waned? The comprehensive and advanced geodetic data from before, during, and after the volcano’s 2022 eruption, unavailable during prior eruptions, offer a means of addressing these questions, which are vital to better understanding and anticipating future eruptive activity and impacts.